The invention relates to a cooling device for vehicles and a method for actuating a cooling device.
It is well known that a refrigerant circuit of an air conditioning system has, when viewed in the direction of flow of the refrigerant, a refrigerant compressor, a condenser, at least one expansion element and one or more evaporators. Vehicle air conditioning systems of many luxury vehicles are equipped with two evaporators, which are connected in parallel. In this case one evaporator is allocated to the front area, and the second evaporator is allocated to the rear area of the passenger compartment. Such vehicle air conditioning systems are usually equipped in such a way that the evaporator or more specifically the cooling circuit, which is responsible for the front area, has a higher priority, in order to implement the corresponding cooling demand requirement for the front area. One example of such an air conditioning system is known from German Patent Publication No. DE 10 2006 053 674 A1.
“Dual evaporator systems” are also common in vehicles. In this case the one evaporator is provided for cooling the passenger compartment; and the other evaporator is provided for cooling the electric and/or electronic components, such as the electric control units, electric energy accumulators, etc.
Here, too, the rotational speed of the compressor is controlled by the cooling demand requirement for the passenger compartment and, in particular, independently of the cooling requirement for the electric accumulator.
One example of a dual evaporator system for cooling the passenger compartment and the electric accumulators is German Patent Publication No. DE 10 2009 033 884 A1. This cooling device comprises a refrigerant compressor; a condenser, which is arranged downstream of the refrigerant compressor in the direction of flow of the refrigerant; a first evaporator, which is arranged downstream of the condenser and is intended for cooling the electric accumulators; and a second evaporator, which is arranged parallel to the first evaporator and is intended for cooling the passenger compartment, wherein the evaporator capacity of the second evaporator can be adjusted by a corresponding valve.
Especially in the case of vehicles, equipped with high voltage accumulators for storing electric energy, optimal cooling of these high voltage accumulators is absolutely mandatory, because the thermal management of electric accumulators is crucial for the service life and safety during on-going operations. For this purpose the lithium ion cells have to stay in an ideal operating temperature range between 20° C. and 40° C.; and all of the cells have to be operated homogeneously in a range of 5 K.
If at this point the cooling demand for the passenger compartment of the vehicle is less than the cooling demand for the electric accumulators or if under some circumstances there is no cooling demand at all for the passenger compartment (for example, in the winter), then the cooling capacity or more specifically the necessary refrigerant mass flow for the electric accumulators is missing. Consequently the temperature of the electric accumulators rises; and, in addition, the temperature spread in the electric accumulator is negatively affected.
At this point the object of the present invention is to provide a cooling device for vehicles and a method that is intended for controlling a corresponding cooling device and that always enables an optimal cooling management of the electric accumulator.
This engineering object is achieved by means of a method and an apparatus for controlling and/or regulating a cooling device for vehicles, the cooling device having a refrigerant compressor, a condenser downstream of the refrigerant compressor, a first evaporator downstream of the condenser for cooling the air to be supplied to the passenger compartment, and a second evaporator parallel to the first evaporator, where a control unit controls the refrigerant compressor as a function of the higher of the cooling demand for the passenger compartment and/or a cooling demand for the electric accumulator.
The starting point of the method according to the invention is a cooling device that is intended for vehicles and that comprises a refrigerant compressor; a condenser, which is arranged downstream of the refrigerant compressor in the direction of flow of the refrigerant; a first evaporator, which is arranged downstream of the condenser and is intended for cooling the air to be supplied to the passenger compartment; and a second evaporator, which is arranged parallel to the first evaporator and is intended for cooling an electric accumulator. Furthermore, there is a control unit that drives or controls at least the refrigerant compressor.
The essence of the method according to the invention lies in the fact that the refrigerant compressor is driven in different ways as a function of a cooling demand requirement for the passenger compartment and/or a cooling demand requirement for the electric accumulator. Correspondingly the invention provides that the refrigerant compressor is driven or controlled on the basis of the higher cooling demand requirement, so that an adequate refrigerant flow for both evaporators is always provided.
In order to be able to ensure that, nevertheless, each requirement is met—that is, each requirement can be implemented—for example, based on a high cooling demand requirement of the one evaporator in relation to the other evaporator, the cooling device according to the invention comprises not only the aforementioned components, but also in addition a first electric valve, which can be driven between the condenser and the second evaporator and which is intended to have an effect on the evaporator capacity of the first evaporator, and a second electric valve, which can be driven between the condenser and the second evaporator and which is intended to have an effect on the evaporator capacity of the second evaporator. The two electric valves are designed advantageously as solenoid valves.
If at this point the cooling unit comprises at least one of the two valves (a first electric valve, which can be driven between the condenser and the first evaporator and which is intended to have an effect on the evaporator capacity of the first evaporator, and/or a second electric valve, which can be driven between the condenser and the second evaporator and which is intended to have an effect on the evaporator capacity of the second evaporator), then in an advantageous further development of the method according to the invention the control unit can drive the first electric valve and/or the second electric valve as a function of the cooling demand requirement for the passenger compartment and/or the cooling demand requirement for the electric accumulator in such a way that the evaporator can be set to the desired refrigerating capacity as a function of the respective requirement, even if under some circumstances the refrigerant compressor is not driven or adjusted with respect to the corresponding requirement.
At this point the method according to the invention can be further developed now in such detail that if, for example, there is a cooling demand requirement for just the electric accumulator alone (that is, there is no cooling demand requirement for the passenger compartment), then the refrigerant compressor is driven at a defined rotational speed required for cooling the energy accumulator and/or that the first electric valve, which has an effect on the cooling capacity of the first evaporator, is closed. This approach can ensure that the electric accumulator is adequately cooled, but that at the same time the passenger compartment is not cooled unintentionally.
If there is a cooling demand requirement for the passenger compartment, but it is less than the cooling demand requirement for the electric accumulator, then the refrigerant compressor is driven in a manner analogous to above at a defined rotational speed required for cooling the energy accumulator. However, at the same time the first electric valve, which has an effect on the cooling capacity of the first evaporator, is not completely closed, but rather is driven in such a way that a cooling capacity, which is reduced relative to the other when the first valve is open, is achieved, in particular in such a way that the cooling demand requirement for the passenger compartment is achieved.
In the third application, where the cooling demand requirement for the passenger compartment is higher than the cooling demand requirement for the electric accumulator, then the refrigerant compressor is regulated (in a manner analogous to the state of the art) on the basis of the cooling demand requirement for the passenger compartment; and/or the second electric valve, which has an effect on the cooling capacity of the second evaporator is driven in such a way that a cooling capacity, which is reduced relative to the other when the second valve is open, is achieved, in particular in such a way that the cooling demand requirement for the accumulator is achieved.
Such an embodiment of the control and/or regulating strategy for the cooling device, comprising two evaporators, can ensure a cooling or more specifically a cooling capacity of the respective evaporator that is adjusted exactly to the respective needs.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.